The poet Robert Frost wrote, “good fences make good neighbors”. If you’d never read his poem, Mending Wall, you might think he liked fences. You would be wrong. The poem is actually about the opposite.
One of the dichotomies of product design is about fences. It’s a problem faced by companies as big as Microsoft and Apple (Apple likes fences, Microsoft not so much), and as small as PS Audio (we’re on the fence about it to make a pun).
Interface fences are needed. Boundaries and standards are set to ensure the proper interface of equipment with the outside world. As in any neighborhood, we all have to agree on some level or sources would not interface with preamps and amps.
One of my readers cried out when I suggested an end-to-end system approach to building our new loudspeakers. “But I like to mix and match equipment. It’s part of the fun of our hobby.” Indeed, our customers run the gamut from tear-the-walls-down tweakers to folks who like their fences.
There’s no way to keep everyone happy. This we know. I think the secret to great products lies in the notion of maintaining outside accessibility of equipment while, at the same time, offering a PS-specific connection scheme. It’s an idea that’s been bubbling in me for some time. Not fully formed yet, but slowly creeping in.
Good fences make good neighbors as long as they aren’t impenetrable walls.
For those interested, here is how an audio power amplifier works.
Peeking under the covers
It seems I may be alone in my enthusiasm to read about high dynamic range loudspeakers and systems in these blog posts so we’ll move on. That’s fine, it’s just that I am currently immersed in the subject because of our work on the new line of Arnie Nudell speakers. We’ve had some excellent work finished by our driver manufacturer including a new midrange ribbon that has me swooning!
That said, I’ll keep on getting excited about high efficiency, high dynamic range solutions, but meanwhile, we’ll switch gears on these posts.
One question I get asked a lot is how a power amplifier works. Generally, the question comes up because power amplifiers seem somewhat of a mystery. Big, heavy boxes, with collections of strange components inside.
To start off the discussion let’s imagine the use case for a power amp—one we’re all familiar with: an input to connect the output of the preamp or DAC, and an output that connects to loudspeakers. What happens in between? We know a preamp is incapable of driving a speaker because it doesn’t have an essential element. Wattage. So, what happens? How does the power amp take the weak output signal from the preamp and give it wattage, muscle, power?
Let’s start with a simple diagram of a power amplifier.
Note there are 3 blocks. An input amplifier (U1) an output amplifier (U2) and a power supply. These are the three critical elements within any analog power amplifier. The 3 elements are:
- Voltage gain stage
- Current gain stage
- Power supply
Tomorrow we’ll start with the voltage gain stage.